DE102016109456A1 - Method for producing a temporomandibular joint endoprosthesis or an implant for the treatment of bony deficits or defects of the facial and cranial skull and other bony defects in the body region - Google Patents

Abstract

A method for producing a temporomandibular joint endoprosthesis, skull prosthesis or body part prosthesis, in which in a first step, an image of the prosthesis to be generated is produced, then in a computer-aided machining process using the image of a ceramic blank, a size-adjusted prosthesis blank is prepared and in a subsequent heat treatment the prosthesis blank the jaw joint endoprosthesis, skull prosthesis or body part prosthesis is made.

Description

Method for producing a temporomandibular joint endoprosthesis or an implant for the treatment of bony deficits or defects of the facial and cranial skull and other bony defects in the body region

The invention relates to a method for producing a temporomandibular joint endoprosthesis, a skull implant or body part implant for replacing the original, bony structures.

For the treatment of inflammatory and / or trauma-related and / or tumor-related and / or plant-related defect states or dysfunctions in the region of the temporomandibular joint or other smaller joints in the human body, it is known to partially or completely replace the joint with a prosthesis. In this context, TMJ prostheses are also known.

The natural temporomandibular joint allows both rotation and horizontal displacement of the jaw joint head during oral opening (translation). The shift is u.a. controlled by lateral wing muscles attached to the jaw joint head. If a complete TMJ prosthesis is used, which is designed in the form of a ball joint and has only three degrees of freedom, the function of the wing muscles and thus the possibility of translation is lost.

After implantation of a ball joint-based prosthesis, the jaw can only be rotated about a fixed point on the side of the prosthesis, so that no more translational movement of the jaw is possible, but which is required for grinding movements of the teeth. Therefore, this type of jaw joint prosthesis is uncomfortable for patients and hinders the function of the jaw. It can even lead to damage in the joint grub.

From the EP 0 628 293 B1 For example, a jaw joint prosthesis is known in which the jaw-side prosthesis part is rotatable about a center of rotation that is positioned relative to the support surface of the skull-side prosthesis part such that the center of rotation is below the center of the natural jaw joint head. It is unclear whether, in this case, by what force or by which muscle the horizontal part of the movement is carried out.

This should allow a more natural movement of the jaw.

The previous TMJ prostheses are composed of different materials. For example, sliding elements should consist of a polymer, the condyle of alumina (AL ₂ O ₃ ) and for the base of the skull-side prosthesis part a cobalt-chromium-molybdenum alloy should be used. Screws and posts should preferably consist of a titanium alloy. In this respect, this temporomandibular joint prosthesis has a complex structure and consists of a variety of materials.

There are other TMJ prostheses known which consist mainly or exclusively of titanium alloys.

The previously known TMJ prostheses are either already completely prefabricated or at least present as semi-finished products. Therefore, it has hitherto been necessary to adapt the temporomandibular joint to the temporomandibular joint prosthesis to be used. In this case, it is disadvantageous that, under certain circumstances, the substance worth preserving must be removed from the area of the jaw in order to be able to fit in the temporomandibular joint prosthesis consisting of prefabricated elements. In particular, the approach of the lateral wing muscle (lateral pterygoid muscle) must be removed in this type of joints, resulting in a significant loss of function.

Titanium alloys are known to allow a very good integration into the bone tissue (osseointegration). However, integration or integration of soft tissue is not fully given in titanium alloys. Therefore, titanium alloy prostheses can not form a starting point for soft tissue, such as tendons and muscles.

The invention has for its object to provide a temporomandibular joint endoprosthesis, skull prosthesis or body part prosthesis, which only requires the removal of damaged substance of the temporomandibular joint and which allows a high functionality of provided with the jaw prosthesis temporomandibular joint after completion of the healing process.

This object is achieved with the features of claims 1 and 8. In advantageous embodiments, the dependent claims relate.

In the method according to the invention for producing a temporomandibular joint endoprosthesis, skull prosthesis or partial body prosthesis, in a first step an image of the prosthesis to be produced is produced, then a size-adapted prosthesis blank is produced in a computer-aided machining process by means of the image from a ceramic blank and is subsequently heat-treated made from the prosthesis blank the TMJ endoprosthesis, skull prosthesis or body part prosthesis.

If necessary, an image of the bony skull is first created. Based on existing data, the substance to be removed is determined and then the endoprosthesis to be produced is constructed as a template in the form of a plastic model. The template forms a positive shape, from which by scanning the shape of the original a digital image of the prosthesis to be generated can be generated. It is advantageous that based on the template, a simulation of the upcoming operation can be performed first. The simulation can be carried out directly on the template or computer-aided.

In the computer-aided simulation, the existing data of the skull image and the scanned template can be used. After completion of the simulation, the template can be adapted if the result of the simulation was not satisfactory. Subsequently, the revised template is scanned again and the simulation is performed again if necessary. If the result of the simulation is positive, the image is used to make the denture blank.

However, it is also conceivable that the template is produced exclusively as a computer model. In this case, the modeling and also the simulation based on the template are computer-aided. The production of a plastic model is omitted here.

A particular advantage results from the fact that the temporomandibular joint endoprosthesis, skull prosthesis or body part prosthesis is produced after presentation of the image. Thus, the shape of the prosthesis is determined by the individual temporomandibular joint situation. The particular advantage here is that only damaged or diseased substance has to be removed from the TMJ by maxillofacial surgery. It is not necessary to adapt the temporomandibular joint to a prefabricated TMJ prosthesis and to remove substance worth preserving. Each temporomandibular joint endoprosthesis, skull prosthesis or body part prosthesis according to the invention forms a unique specimen and is precisely adapted to the individual situation of the temporomandibular joint. It is particularly advantageous that the approach of the wing muscle can be obtained, while the rest of the destroyed joint head can be replaced. In this respect, the attaching muscles can be obtained intraoperatively.

The temporomandibular joint endoprosthesis, skull prosthesis or body part prosthesis according to the invention can be well integrated into the surrounding soft tissue and healed firmly with the underlying bone. The completion of the healing process guarantees high functionality of the mandibular joint endoprosthesis. Another advantage is that the approach of the wing muscles can be left out, so that the natural rotational sliding movement can be maintained.

The inventive method is particularly suitable for the production of skull prostheses, for example in the area of the zygomatic bone, the forehead, the chin and the angle of the jaw. Another field of application is the production of partial body prostheses of the iliac crest. On the whole, the method according to the invention is particularly advantageous for the production of prostheses in the field of plastic surgery.

The mandibular joint endoprosthesis, skull prosthesis or body part prosthesis according to the invention consists exclusively of a ceramic material. This has the particular advantage that, on the one hand, integration into the bone tissue (osseointegration) is provided and, moreover, there is also an integration into the soft tissue surrounding the temporomandibular joint or the facial bones. The integration of the soft tissue results in complete functionality of the temporomandibular joint after complete healing. The temporomandibular joint endoprostheses, skull prostheses or body part prostheses grow together firmly on the bony surface (osseointegration) and integrate into the soft tissue without irritation. Another advantage is that the individual preparation of the temporomandibular joint endoprosthesis, skull prosthesis or body part prosthesis, an aesthetic approximation of the temporomandibular joint to the original situation is possible.

The ceramic blank consists of a ceramic powder which is pressed into an ingot with an organic binder, for example polyacrylic acid. Such a ceramic blank, also referred to as zirconia powder compact, has a high porosity and low intrinsic strength. The consistency of the ceramic blank is chalk-like. This makes it possible to edit the ceramic blank with cutting tools. The low strength of the ceramic blank results in short processing times and low tool wear.

In the subsequent heat treatment, the ceramic material compacts and the organic binder is removed from the matrix of the ceramic material. The prosthesis blank shrinks by reducing the porosity and structural changes and thus loses volume. Therefore, it is necessary to make a size-adjusted prosthesis blank from the ceramic blank. After completion of the heat treatment results from the prosthesis blank, the ceramic jaw joint endoprosthesis, skull prosthesis or body part prosthesis, which has a high hardness and high strength. For example, the Bending strength of zirconia higher than that of titanium alloys known for prostheses.

Preferably, the ceramic blank is formed of oxide ceramic. Oxide ceramics are single-phase ceramic materials without glass phase. Although oxide-forming metals are among the less noble metals, at the same time they have a high oxidation potential and the oxides are very stable.

In a preferred embodiment, the ceramic blank comprises zirconium dioxide (ZrO ₂ ). Zirconia is non-magnetic, highly resistant to acids and alkalis, and has high resistance to chemical, thermal and mechanical influences. For stabilization, the sintering powder forming the ceramic blank usually still has stabilizer additives in the form of other metal oxides. The use of zirconium dioxide in the medical field is already known. Due to its high biocompatibility, zirconium dioxide is already being used in the manufacture of condylar heads for hip replacements. It is also known to form metal-free dental implants or dental prostheses made of zirconium dioxide. However, in the case of rod ends and implants, prefabricated components are always used.

Alternatively, it is conceivable that the ceramic blank comprises aluminum oxide (AL ₂ O ₃ ). Like zirconia, alumina is biocompatible and has high strength following post heat treatment. However, the bending strength of alumina is lower than that of zirconia.

Preferably, the ceramic blank is subjected to an upstream heat treatment. If the sintered powder forming the ceramic blank, the powdered ceramic material, is compressed in block form with only an organic binder, a ceramic blank with a chalky-white consistency is produced, which, while easy to process, is difficult to handle at the same time. Due to the soft consistency, there is a risk that the processed ceramic blank will be destroyed before the subsequent heat treatment. Through the upstream heat treatment, the ceramic blank is preconsolidated. Although this prolongs the milling times and tool wear increases, the prosthesis blank made from the ceramic blank is much more stable and easier to handle. This can prevent the prosthesis blank from being destroyed by incorrect handling before the subsequent heat treatment.

After completion of the resective treatment, in which the medically necessary destroyed material has been removed from the temporomandibular joint, the TMJ area is preferably detected electronically by means of a scanner. Subsequently, an image of a temporomandibular joint endoprosthesis to be created is created by means of a CAD process (computer-aided design) from the scan data. In this case, the shrinkage process of the downstream heat treatment is taken into account, so that a size-adjusted prosthesis blank can be produced, from which the appropriate tailor-made temporomandibular joint endoprosthesis is produced after completion of the downstream heat treatment.

Alternatively, it is conceivable that a model of the temporomandibular joint endoprosthesis, skull prosthesis or partial body prosthesis to be created is created on the basis of a previously prepared finding, for example on the basis of DVT data (digital volume tomography). The model is preferably made of plastic. This has the advantage that the position and shape of the temporomandibular joint endoprosthesis, skull prosthesis or partial body prosthesis to be produced can be checked prior to the operation on the basis of the model in the intended operating area. In this case, changes can still be made to the model such that the resection is performed on the model in the sense of an OP simulation. Based on the possibly modified model, a template for the machining process is finally created.

The thus created electronic model of the temporomandibular endoprosthesis or skull prosthesis or partial body prosthesis is then preferably read into a computer-controlled milling machine, so that as a cutting tool preferably a three-dimensionally working CNC milling machine is used. CNC (Computerized Numerical Control) -controlled machine tools enable computer-controlled numerical control of machine tools and thus in this case the production of prosthesis blanks with high accuracy. The combination of electronically recorded scan data and the electronic modeling of the image in a CAD process results in a consistently electronic production process of the prosthesis blank. This process, also referred to as CAM (computer-aided manufacturing), enables the cost-effective production of prosthesis blanks with high accuracy and at the same time complex shaping. As a result, it is possible to produce jaw joint endoprostheses, skull prostheses or body part prostheses adapted to the individual application.

The downstream heat treatment is preferably a sintering process. In the sintering process, the prosthesis blank is heated for several hours, for example, for eight hours, temperatures of about 1,000 ° C, for example, a temperature exposed to 1,400 ° C. In this heat treatment, the prosthesis blank shrinks by up to 25% by volume due to the reduction in porosity and microstructural changes in the crystalline structure of the ceramic material. After completion of the heat treatment, the prosthesis blank is transformed into a ceramic jaw joint endoprosthesis, skull prosthesis or body part prosthesis with high strength, excellent biocompatibility and good integration into the bone tissue and the adjacent soft tissue.

The jaw joint endoprosthesis, skull prosthesis or body part prosthesis made of ceramic material produced by the method according to the invention has the advantage of a good osseointegration and moreover also the advantage of a good integration into the soft tissue. In addition, the ceramic jaw joint endoprosthesis, skull prosthesis or body part prosthesis has a high strength, in particular bending strength on. This is particularly important because high mechanical loads occur in the region of the temporomandibular joint during the chewing process. By the simultaneous good integration of the ceramic TMJ endoprosthesis, skull prosthesis or body part prosthesis in both the bone and in the soft tissue results in completion of the healing process, a high functionality of the provided with the prosthesis temporomandibular joint. At the same time a high aesthetic can be ensured by the individual shaping of the prosthesis, which has particular relevance especially in the facial area.

In an advantageous embodiment recesses for receiving fastening means are introduced into the ceramic material in the temporomandibular joint endoprosthesis, skull prosthesis or body part prosthesis. These recesses preferably have the shape of holes, wherein the outwardly facing portion of the recess may be configured conical. This allows the complete inclusion of helical fasteners, such as titanium screws. By means of the fastening means, the temporomandibular joint endoprosthesis, skull prosthesis or body part prosthesis can be fixed in place in the remaining lower jawbone. This facilitates osseointegration of the TMJ endoprosthesis, skull prosthesis or body part prosthesis. Fasteners are preferably titanium screws, which also have a good osseointegration. After completion of the healing process but also the endoprosthesis itself is firmly anchored in the bone tissue. Alternatively, however, prefabricated screws can also be used zirconia.

The method according to the invention for producing a temporomandibular joint endoprosthesis, a skull prosthesis or a partial body prosthesis is explained in more detail below:
First, a ceramic blank is provided. The ceramic blank consists of powdered ceramic material, for example aluminum oxide (Al ₂ O ₃ ), preferably zirconium dioxide (ZrO ₂ ). The powdery material is pressed into a block and held in shape by means of a polyacrylic acid-based organic binder. Before the machining, the ceramic blank may be subjected to an upstream heat treatment. This upstream heat treatment is also referred to as Vorbrand. The pre-firing is associated with a low shrinkage rate and causes a preconsolidation of the powdered ceramic material. This simplifies the handling of both the ceramic blank and the denture blank produced by the machining process.

A computer image of the prosthesis to be generated is created by means of a 3D scanner and a subsequent CAD process. The dimension of the image takes into account the shrinkage process that occurs during the subsequent heat treatment. In this respect, the prosthesis blank is sized in comparison to the later TMJ endoprosthesis, skull prosthesis or body part prosthesis.

As an alternative to the scan data, a template of the temporomandibular endoprosthesis, skull prosthesis or partial body prosthesis to be produced can first be produced on the basis of X-ray images and the like, which after a possible modification, for example after a simulation, is converted into a computer-readable model. The simulation can be performed using the template or computer based on existing data from the skull and the template. The template is preferably made of a plastic. It is conceivable that the template is generated by means of a 3D printer. Alternatively, the preparation of the template but also done by hand or it is exclusively created a template in the form of a computer model.

The computer-generated image of the temporomandibular joint endoprosthesis, skull prosthesis or partial body prosthesis to be produced is placed in a computer-controlled three-dimensional milling machine, where the prosthesis blank is produced from the ceramic blank by means of the electronic image by means of the cutting process. Subsequently, the prosthesis blank is subjected to a subsequent heat treatment, in which the temporomandibular joint is removed from the prosthesis blank. Endoprosthesis or the skull prosthesis or body part prosthesis arises. The downstream heat treatment involves a heat treatment over a period of eight hours at a temperature of 1400 ° C.

In the computer-aided modeling of the image of the temporomandibular joint endoprosthesis, skull prosthesis or body part prosthesis recesses for fasteners are taken into account. These are designed in the form of cylindrical bores, wherein the outwardly facing portion of the bores for receiving screw heads is conical. The recesses serve to receive fastening means, preferably titanium screws or alternatively screws made of a ceramic material.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 0628293 B1 [0006]

Claims (10)

 A method for producing a temporomandibular joint endoprosthesis, skull prosthesis or body part prosthesis, in which in a first step, an image of the prosthesis to be generated is produced, then in a computer-aided machining process using the image of a ceramic blank, a size-adjusted prosthesis blank is prepared and in a subsequent heat treatment the prosthesis blank the jaw joint endoprosthesis, skull prosthesis or body part prosthesis is made. A method according to claim 1, characterized in that the ceramic blank comprises zirconium dioxide. A method according to claim 1, characterized in that the ceramic blank comprises alumina. Method according to one of claims 1 to 3, characterized in that the ceramic blank was subjected to an upstream heat treatment. Method according to one of claims 1 to 4, characterized in that the generation of the image comprises a combined scanning and CAD process. Method according to one of claims 1 to 4, characterized in that for generating the image, a model is made. Method according to one of claims 1 to 6, characterized in that the computer-aided machining process is a CNC-controlled three-dimensional milling process. Method according to one of claims 1 to 7, characterized in that the downstream heat treatment is a sintering process.  Tibial joint endoprosthesis, skull prosthesis or body part prosthesis made of ceramic material according to a method according to one of the preceding claims. Tibial joint endoprosthesis, skull prosthesis or body part prosthesis according to claim 9, characterized in that recesses for receiving fastening means are introduced into the ceramic material.